Ammonium chloride solution for fishless cycling_x000D_ use with one & only nitrifying bacteria_x000D_ this bottle of reagent grade ammonium chloride is for use when fishless cycling. Concentration is 40 mg/ml of total ammonia-nitrogen (tan). Dose 4 drops per gallon of aquarium water.* Use with one and only nitrifying bacteria. Generally during a fishless cycle you need to add ammonium chloride to your tank 3 times so: a 2 ounce (60 ml) bottle will cycle 100 gallons (359 liters)_x000D_ a 4 ounce (120 ml) bottle will cycle 200 gallons (757 liters)_x000D_ a 8 ounce (480 ml) bottle will cycle 400